Bath Remodel Questions - Is This a Good Design?

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New Member
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Columbia, SC
Hello, friends,

Frequent reader over the last 20 years or so. First time poster. I would appreciate advice on whether my plumbing changes are correct. I'm under IPC.

I am remodeling a full bath on a 4" slab on grade. The toilet needs to be relocated to a better spot, as does the vanity. Thankfully, both are close to the exterior wall. There's a 3" PVC drain line a few feet outside the exterior wall. That line has one bath (toilet, lav and shower) and the kitchen sink on it. For a number of reasons, I believe my best approach here will be to cut the slab and connect the relocated toilet and lav to that 3" drain line.

I am also making changes to accommodate the bathroom above. Instead of a single lav, it will have a double.

I've drawn out the plumbing system for the entire house (attached). The changes are marked in blue. I appreciate your patience with my crude drawings!

Are my proposed changes correct? Any advice?


  • house plumbing diagram.pdf
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Jeff H Young

In the Trades
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1st floor tub is wet vented from floor above thats not right. 1st floor toilet and lav that get revented only need 1 1/2" in your code but 2 inch is fine. 2nd floor 1/2 bath and laundry venting is wrong , along with the tub. master bath toilet 1 1/4 ne3ver heard of that I think your code allows 1 1/2" vent , master double lavs is ok but why a 2 inch vent? kitchen sink is great!
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